From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko Stuebner Subject: Re: [PATCH v3 06/14] Documentation: drm/bridge: add document for analogix_dp Date: Mon, 24 Aug 2015 15:03:05 +0200 Message-ID: <18468783.Lfl8UEMQ1s@phil> References: <1439995728-18046-1-git-send-email-ykk@rock-chips.com> <55DA9B72.1030804@samsung.com> <55DB1281.9070502@rock-chips.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <55DB1281.9070502@rock-chips.com> Sender: linux-samsung-soc-owner@vger.kernel.org To: Yakir Yang Cc: Krzysztof Kozlowski , Rob Herring , Sean Paul , Takashi Iwai , dri-devel , Andrzej Hajda , Gustavo Padovan , "linux-samsung-soc@vger.kernel.org" , Vincent Palatin , Kishon Vijay Abraham I , linux-rockchip@lists.infradead.org, Russell King , Thierry Reding , "devicetree@vger.kernel.org" , Pawel Moll , Ian Campbell , David Airlie , Doug Anderson , Inki Dae , Ajay kumar , Rob Herring , linux-arm-kern List-Id: devicetree@vger.kernel.org Hi Yakir, Am Montag, 24. August 2015, 20:48:01 schrieb Yakir Yang: > =E5=9C=A8 08/24/2015 12:20 PM, Krzysztof Kozlowski =E5=86=99=E9=81=93= : > > On 24.08.2015 11:42, Yakir Yang wrote: > >> Hi Krzysztof, > >>=20 > >> =E5=9C=A8 08/23/2015 07:43 PM, Krzysztof Kozlowski =E5=86=99=E9=81= =93: > >>> 2015-08-24 8:23 GMT+09:00 Rob Herring : > >>>> On Wed, Aug 19, 2015 at 9:50 AM, Yakir Yang = wrote: > >>>>> Analogix dp driver is split from exynos dp driver, so we just > >>>>> make an copy of exynos_dp.txt, and then simplify exynos_dp.txt > >>>>>=20 > >>>>> Beside update some exynos dtsi file with the latest change > >>>>> according to the devicetree binding documents. > >>>>=20 > >>>> You can't just change the exynos bindings and break compatibilit= y. Is > >>>> there some agreement with exynos folks to do this? > >>>=20 > >>> No, there is no agreement. This wasn't even sent to Exynos mainta= iners. > >>=20 > >> Sorry about this one, actually I have add Exynos maintainers in ve= rsion > >> 1 & version 2, > >> but lose some maintainers in version 3, I would fix it in bellow > >> versions. > >>=20 > >>> Additionally the patchset did not look interesting to me because = of > >>> misleading subject - Documentation instead of "ARM: dts:". > >>>=20 > >>> Yakir, please: > >>> 1. Provide backward compatibility. Mark old properties as depreca= ted > >>> but still support them. > >>=20 > >> Do you mean that I should keep the old properties declare in > >> exynos-dp.txt, > >> but just mark them as deprecated flag. > >=20 > > That is one of ways how to do this. However more important is that > > driver should still support old bindings so such code: > > - if (of_property_read_u32(dp_node, "samsung,color-space", > > + if (of_property_read_u32(dp_node, "analogix,color-space", > >=20 > > is probably wrong. Will the driver support old DTB in the same way = as it > > was supporting before the change? >=20 > Okay, I got your means. So document is not the focus, the most import= ant > is that > driver should support the old dts prop. If so the new analogix dp dri= ver > should keep > the "samsung,color-space", rather then just mark it with [DEPRECATED]= flag. >=20 > But from your follow suggest, I think you agree to update driver code= , > and just mark > old prop with deprecated flag. If so I think such code would not be w= rong >=20 > - if (of_property_read_u32(dp_node, "samsung,color-space", > + if (of_property_read_u32(dp_node, "analogix,color-space", In a generic driver, the property should have either none, or the analo= gix=20 prefix. But DT-properties need to be backwards compatible, meaning an o= lder=20 Exynos devicetree should run unmodified with a newer kernel. So the common course of action is to mark the old one as deprecated but= still=20 test for both, so something like: if (of_property_read_u32(dp_node, "analogix,color-space", &dp_video_config->color_space)) if (of_property_read_u32(dp_node, "samsung,color-space", &dp_video_config->color_space)) { dev_err(dev, "failed to get color-space\n"); return ERR_PTR(-EINVAL); }